We will continue sequencing nucleotide changes in the lac promoter region produced by mutations, and we will try to determine where lac mRNA synthesis initiates in vivo both in the wild type and several promoter "up" mutants. We will continue our efforts to define completely the steps in the synthesis of bacteriophage T4 tRNAs. Bibliographic references: Nucleotide Sequence Determination of Bacteriophage T4 Species I RNA. Gary V. Paddock and John Abelson. J. Biol. Chem., 250, 4185-4206 (1975); Nucleotide Sequence Determination of Bacteriophage T2 and T6 Species I RNA. Gary V. Paddock and John Abelson. J. Biol. Chem., 250. 4207-4219 (1975).